It was launched in London on June 30, 1937 after a committee examined how operators could easily identify emergency calls, following the deaths of five women in a fire at surgeon’s home two years previously.

The choice of 999 was because in the dark or in dense smoke, 999 could be dialled on the old rotary telephones by placing a finger against the dial stop and rotating the dial to the full extent three times.

A 1937 poster teaches people how to dial 999 (Picture: Geoff Robinson)

Before the service’s introduction, callers on an automated exchange would dial 0 and ask the operator to contact the emergency services.

The first week of the service saw it take more than 1,000 calls. They were indicated by red lamps and a loud klaxon, which led to fears the noise would cause nervous strain to telephonists. The first call was made by a Mrs Beard in Hampstead, north London and led to the arrest of burglar Thomas Duffy.

Glasgow was the second city to have the service in 1938 and it was extended to all major towns and cities ten years later.

A training photo shows how calls are received in 1948 (Picture: Geoff Robinson)

Now, there are about 85,000 emergency 999 calls each day and 31million a year. Slightly more than half of these are for the police.

The early hours of New Year’s Day are traditionally the busiest time when up to 13,500 calls can be received each hour. BT’s Warren Buckley said: ‘It’s not only the world’s oldest emergency call service, it’s also one of the world’s most respected and admired services.

‘Our 999 operators are the first port of call for people seeking help and we’re very proud of the part they have played in this essential service.’